Vaccines have been used to prevent infectious diseases, and the successful global elimination of smallpox was attained only through vaccination. However, not all preventive vaccines are as effective as vaccinia; therefore developing measures to improve the quality of vaccines, as well as decreasing the number of inoculations of vaccines to be given are necessary. Aside from preventive vaccines, therapeutic vaccines used for active immunization of patients with chronic bacterial or viral diseases (Tuberculosis, Herpes simplex, Viral hepatitis B, AIDS etc.) have also been developed. There are two categories of therapeutic vaccines, namely specific and non-specific therapeutic vaccines. Immunization with non-specific therapeutic vaccines (e.g. BCG, Corynebacterium parvum etc.) can induce non-specific host immune responses, especially cell-mediated immune responses, which showed some effects, but were usually not potent enough to terminate chronic infections. Since specific therapeutic vaccines can induce specific humoral and cellular immune responses in infected hosts, therefore specific therapeutic vaccines are more preferable. Presently, specific therapeutic vaccines can be grouped as: (1). Inactivated or killed whole microbial vaccines. Usually specific strains of microbes were selected and were inactivated or killed for preparation. (2). Recombinant vaccines expressing specific microbial antigen(s). Recombinant technologies were employed to express one or more microbial antigen(s). (3). Chimeric vaccines: Chimeric genes constructed with genes coding for specific microbial antigens fused with genes coding for cytokines (interferons or interleukin-2 etc.) were expressed as fusion proteins and used for active immunization. (4). Synthetic peptide vaccines: Epitopes from microbes were selected and were either used for preparation of synthetic peptides or used for preparation of chimeric peptides (with adjuvants or cytokines added) for active vaccination. (5). Microbial antigen-antibody complex: Appropriate ratio of microbial antigen and antibody complex was used to generate more potent immune responses. (6). Nucleic acid (DNA or polynucleotide, or recombinant DNA vaccine) vaccines: Fragments of genes coding for the protective antigens of microbes were cloned into expression vectors and these recombinant-vector nucleic acid vaccines were used for immunization. Significant enhanced humoral, and especially cellular immune response could be generated by this approach of immunization. Appropriate method of recombinant DNA vaccine delivery into tissues (muscles, skin) is critical, in order to induce effective immune responses. In addition, minimizing the amount of nucleic acid used for induction of effective immune responses is desirable.
Davis H L et al. (Human Molecular Genetics 1993;2:1857) demonstrated that by using a vector DNA which contains the encoding gene fragment of hepatitis B surface antigen for DNA-based immunization in mice, secretion of hepatitis B surface antigen and high levels of circulating antibody was detected. A number of publications appeared in the past few years in regard to various microbial nucleic acid (or DNA) vaccination. Among these, Macini M et al (Proc. Natl. Acad. Sci. USA 1996; 93:12496) reported by DNA-based immunization in a transgenic mouse model of the hepatitis B surface antigen chronic carrier state, resulted in complete clearance of circulating HBsAg, which raised the possibility of designing effective ways for treatment of chronic hepatitis B. In PCT WO 95/11307 (Nucleotide vector, composition containing such vector and vaccine for immunization against hepatitis) and PCT WO 95/20660 (Immunization by inoculation of DNA transcription unit) etc., different composition and routes of nucleic acid immunization have been employed; however, preparation of antigen-antibody-recombinant DNA complex vaccine and its immunogenicity has not been mentioned in such literature.
Enhanced immune responses were shown by immunization using microbial antigen complexed to specific antibodies, as reported in Venezuelan Equine Encephalomyelitis Virus (Houston W E et al. J Inf Dis 1977;155:600), tetanus toxoid (Stoner R D et al. J Immunol 1963;91:761), hepatitis B surface antigen (Chang T S. Immunology Today 1985;6:245). In addition, mice immunized with solid-matrix-antibody-antigen complexes of multivalent antigens (Herpes simplex virus glycoprotein D, influenza virus HA protein, simian virus HN proteins etc.) showed vigorous humoral and cellular immune responses (Randall R E et al. J Virol 1989;63:1808). Such published manuscripts have described only the use of polyclonal or monoclonal animal antibodies complexed to antigens to induce immune responses. Immune responses were improved, but there was no description of using the complex for treatment of chronic persistent infections. One of the present inventors patented (in China) and published in the literature using hepatitis B vaccine complexed to human specific immunoglobulins against Hepatitis B vaccine (HBIG) to treat chronic hepatitis B patients (Wen Y M et al. Lancet 1995;345:8964). To date, no antigen-antibody complex including incorporation of recombinant plasmid DNA as a complex vaccine has been described.